1. Field of the Invention
The present invention relates to a communication device and a method used in a wireless communication system and related communication device, and more particularly, to a communication device and method of handling communication operations in a licensed frequency band and an unlicensed frequency band in a wireless communication system.
2. Description of the Prior Art
A long-term evolution (LTE) system developed by the 3rd Generation Partnership Project (3GPP) is a successor of the universal mobile telecommunication system (UMTS) for further enhancing performance of the UMTS to satisfy increasing needs of data transmission. The LTE system includes a new radio interface and a new radio network architecture that provides high data rate, low latency, packet optimization, and improved system capacity and coverage. In the LTE system, a radio access network known as an evolved universal terrestrial radio access network (E-UTRAN) includes multiple evolved Node-Bs (eNBs) for communicating with multiple user equipments (UEs), and for communicating with a core network including a mobility management entity (MME), a serving gateway, etc., for Non-Access Stratum (NAS) control.
In general, WiFi transmission and WiFi reception may be performed on a carrier in an unlicensed frequency band. On the other hand, in the LTE system, the UE may perform a UL transmission and/or a downlink (DL) reception with the network in a licensed frequency band.
In order to ease load of network traffic in the LTE system, network operators offload part of the network traffic to the unlicensed frequency band by deploying a large amount of WiFi Access Points (APs). However, deploying numerous WiFi APs may not always achieve expected network performance improvement. It is preferable that a communication interfacing unit of the communication device in the LTE system can operate the UL transmission and/or the DL reception in the unlicensed frequency band.
However, when the LTE system is allowed to operate in an unlicensed frequency, the transmissions/receptions from the LTE system and other technologies (e.g., WiFi and Bluetooth) may interfere with each other as they are all in the same unlicensed frequency. Hence, how to handle the communication operations in the licensed frequency band and the unlicensed frequency band for a communication device in the LTE system is an important topic to be discussed.